Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Tanigawa, Hiroyasu; Sokolov, M. A.*; Sawahata, Atsushi*; Hashimoto, Naoyuki*; Ando, Masami; Shiba, Kiyoyuki; Enomoto, Masato*; Klueh, R. L.*
Journal of ASTM International (Internet), 6(5), 10 Pages, 2009/05
The master curve (MC) method works when the transition fracture toughness values follow the MC, and once the value is scaled properly, the MC is usually independent of the type of steel or the type of test specimen. This method is very much depending on the assumption that the fracture initiation points are homogeneously distributed and its initiation mechanism is independent on test temperature. The reduced-activation ferritic/martensitic steels (RAFs), such as F82H (Fe-8Cr-2W-0.2V-0.04Ta), has Al
O
Ta(V,Ti)O composite inclusions, or simple Ta(V)O inclusions, and shows inhomogeneous distribution, and it was revealed that that RAFs which contain Ta could initiate the facture in the different mechanism at lower temperature as the composite inclusions become fragile, and this should be considered when the toughness measured with small size toughness specimen which is usually tested at lower temperature.
Sawahata, Atsushi; Tanigawa, Hiroyasu; Enomoto, Masato*
Nihon Kinzoku Gakkai-Shi, 72(3), p.176 - 180, 2008/03
Times Cited Count：14 Percentile：59.37(Metallurgy & Metallurgical Engineering)no abstracts in English
Tanigawa, Hiroyasu; Sawahata, Atsushi; Sokolov, M. A.*; Enomoto, Masato*; Klueh, R. L.*; Koyama, Akira*
Materials Transactions, 48(3), p.570 - 573, 2007/03
Times Cited Count：22 Percentile：71.95(Materials Science, Multidisciplinary)The effects of microstructural inhomogeneity of F82H-IEA was investigated focusing on inclusion. It turned out that Ta does not form MX precipitates, but it forms complex AlO;Ta(V,Ti)O inclusions, or simple Ta(V)O inclusions. The complex inclusions are rather dominant in the plate obtained from the bottom of the ingot, but not in the plate from the middle of the ingot. SEM observations also revealed that broken complex inclusions tended to be observed at the crack-initiation site. These results suggest that the scatter of toughness values is correlated with this microstructural inhomogeneity, as the MC method assumes the material has a homogeneous microstructure.
Sawahata, Atsushi; Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Enomoto, Masato*
Nihon Kinzoku Gakkai-Shi, 71(2), p.244 - 248, 2007/02
Times Cited Count：1 Percentile：13.06(Metallurgy & Metallurgical Engineering)Reduced activation ferritic/martensitic steels (RAFs), such as F82H (Fe-8Cr-2W-0.2V-0.04Ta-0.1C), are one of the leading candidates for structural materials of fusion reactors, and it is essential for RAFs R&D to assure its good toughness property for fusion application. In this study, the influence of Ti on impact property was studied based on microstructural analyses and charpy impact tests which were performed against general-purity F82H (0.004Ti-0.0060N) and high-purity F82H (
0.001Ti- 0.0014N). In general-purity F82H, its impact property around DBTT showed both 100% brittle fracture and brittle-ductile, and this tendency is not appeared in high-purity F82H. SEM observation on those brittle fracture surfaces of general-purity F82H revealed the presence of AlO-Ta(V,Ti)O complex oxides at the fracture initiation point. The size distribution analyses of oxides suggest that the complex oxide in general-purity F82H showed a higher number density than in high-purity F82H. In addition to this, EDS analyses showed the complex oxides in general-purity F82H had a strong peak of Ti, but they were not detected in the oxide in high-purity F82H. These results suggest the influence of Ti on complex oxide formation which affects impact property.
Sawahata, Atsushi; Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Enomoto, Masato*
no journal, ,
Reduced activation ferritic/martensitic steels (RAFs), such as F82H (Fe-8Cr-2W-0.2V-0.04Ta-0.1C, in wt%), are one of the leading candidates for structural materials of fusion reactors. Impact property of F82H can be improved by adjusting the amount of tantalum or titanium concentration. On the other hand, it was reported by microstructure analyses of IEA steel that tantalum has a tendency to form oxides and causes a large dispersion of fracture toughness. In this study, the correlation between titanium or tantalum concentration and the impact property were reported focusing on difference in microstructure.
